Nested lists, how I can do this with lambda expression?

Question

Can't really understand how the select extension method works with a list inside another list, like this:

var queries = (from item in list
               from item2 in list.anotherlist
               select item2).ToList<MyType>();

This will not work:

// Gives me a list of List<QueryResult>
var queries = list.Select(item => item.anotherlist).ToList();

Ben · Accepted Answer · 2010-11-28 03:40:42Z

5

The SelectMany operator ought to do the trick - in this case, it takes a list of lists and flattens it:

var queries = list.SelectMany(sublist => sublist).ToList();

answered Nov 28, 2010 at 3:40

Ben

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1 Comment

+1. Just for completeness' sake, I'll add that from … from … select … in a LINQ expression is actually equivalent to SelectMany; it won't translate to Select. See e.g. this query expression translation cheat sheet by Bart de Smet or the C# 3.0 specification, section 7.15.2.4.

Dean Chalk · Accepted Answer · 2010-11-28 09:52:51Z

0

use selectmany

var queries = list.SelectMany(l => l.anotherList).ToList();

answered Nov 28, 2010 at 9:52

Dean Chalk

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